National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8566, Japan.
Mol Ecol. 2011 Feb;20(4):853-68. doi: 10.1111/j.1365-294X.2010.04980.x. Epub 2010 Dec 28.
Many insects are ubiquitously associated with multiple endosymbionts, whose infection patterns often exhibit spatial and temporal variations. How such endosymbiont variations are relevant to local adaptation of the host organisms is of ecological interest. Here, we report a comprehensive survey of endosymbionts in natural populations of the chestnut weevil Curculio sikkimensis, whose larvae are notorious pests of cultivated chestnuts and also infest acorns of various wild oaks. From 968 insects representing 55 localities across the Japanese Archipelago and originating from 10 host plant species, we identified six distinct endosymbiont lineages, namely Curculioniphilus, Sodalis, Serratia, Wolbachia, Rickettsia and Spiroplasma, at different infection frequencies (96.7%, 12.8%, 82.3%, 82.5%, 28.2% and 6.8%, respectively) and with different geographical distribution patterns. Multiple endosymbiont infections were very common; 3.18±0.61 (ranging from 1.74 to 5.50) endosymbionts per insect on average in each of the local populations. Five pairs of endosymbionts (Curculioniphilus-Serratia, Curculioniphilus-Wolbachia, Sodalis-Rickettsia, Wolbachia-Rickettsia and Rickettsia-Spiroplasma) co-infected the same host individuals more frequently than expected, while infections with Serratia and Wolbachia were negatively correlated to each other. Infection frequencies of the endosymbionts were significantly correlated with climatic and ecological factors: for example, higher Sodalis, Wolbachia and Rickettsia infections at localities of higher temperature; lower Wolbachia and Rickettsia infections at localities of greater snowfall; and higher Curculioniphilus, Sodalis, Serratia, Wolbachia and Rickettsia infections on acorns than on chestnuts. These patterns are discussed in relation to potential host-endosymbiont co-evolution via local adaptation across geographical populations.
许多昆虫普遍与多种内共生体共生，其感染模式常常表现出时空变化。这些内共生体的变化如何与宿主生物的局部适应相关，这是一个生态学上的有趣问题。在这里，我们报告了对栗山蛀果象自然种群中内共生体的全面调查，其幼虫是栗属植物的著名害虫，也侵害各种野生栎属橡树的橡实。从来自日本群岛 55 个地点的 968 只昆虫中，这些昆虫来自 10 种宿主植物，我们鉴定出了 6 种不同的内共生体谱系，即 Curculioniphilus、Sodalis、Serratia、Wolbachia、Rickettsia 和 Spiroplasma，它们的感染频率不同（分别为 96.7%、12.8%、82.3%、82.5%、28.2%和 6.8%），地理分布模式也不同。多种内共生体感染非常常见；每个地方种群中的平均每只昆虫有 3.18±0.61（范围为 1.74 到 5.50）种内共生体。有 5 对内共生体（Curculioniphilus-Serratia、Curculioniphilus-Wolbachia、Sodalis-Rickettsia、Wolbachia-Rickettsia 和 Rickettsia-Spiroplasma）在同一宿主个体中共同感染的频率高于预期，而 Serratia 和 Wolbachia 的感染呈负相关。内共生体的感染频率与气候和生态因素显著相关：例如，温度较高的地方 Sodalis、Wolbachia 和 Rickettsia 的感染较高；降雪量较大的地方 Wolbachia 和 Rickettsia 的感染较低；橡实上的 Curculioniphilus、Sodalis、Serratia、Wolbachia 和 Rickettsia 的感染高于栗树上的感染。这些模式与通过地理种群的局部适应进行潜在的宿主-内共生体共同进化有关。
